Piston pump

ABSTRACT

In piston pumps for brake systems used until now, there were often noise problems, from pressure pulsations.  
     In the piston pump for brake systems proposed here, a pulsation-smoothing device ( 40 ) that functions effectively well is provided in the region of the outlet valve ( 24 ). As a result, substantially less noise occurs, and the durability of the piston pump ( 1 ) is substantially better.  
     The piston pump is used essentially in traction-controlled motor vehicle brake systems.

PRIOR ART

[0001] The invention relates to a piston pump as generically defined bythe preamble to claim 1. The piston pump is intended particularly for ahydraulic traction-controlled vehicle brake system.

[0002] German Published, Nonexamined Patent Application DE 42 26 646 A1shows a hydraulic vehicle brake system with a pump, in which a pressuredamper is provided downstream of an outlet check valve. For the pressuredamper provided in the pressure line to have an adequate effect, thepressure damper must be made suitably large. Because of the pressuredamper, the known vehicle brake system is relatively large as well, andincreased production cost is necessary. Upon actuation of the brakepedal, some of the pressure medium positively displaced via the driver'sfoot is forced into the pressure damper. Because the pressure dampermust be relatively large for an adequate effect, upon actuation of thebrake pedal a relatively large quantity of pressure medium has to bepositively displaced, which must be taken into account by suitabledimensioning of the components involved in this process. As a result,the known brake system is rather large in size.

ADVANTAGES OF THE INVENTION

[0003] The piston pump of the invention having the characteristics ofclaim 1 has the advantage that the pulsation-smoothing device quiteeffectively overcomes the pressure pulsations and pressure waves thatotherwise occur in a piston pump. Because of the high effectiveness ofthe pulsation-smoothing device, this device can be made rather smallwhile an adequate effect is nevertheless attained. Since thepulsation-smoothing device can be made rather small, the advantage isattained that the overall piston pump is fairly. This has the advantageof a vehicle brake system that is small overall. Because thepulsation-smoothing device is small because of its good effectiveness,and in particular the storage volume can be kept rather small, theadvantage is attained that upon an actuation of the brake pedal, at mostan insignificant proportion of the pressure medium put under pressure bythe driver's foot is taken up by the pulsation-smoothing device, so thatthere is practically no negative effect from the pulsation-smoothingdevice on the mode of operation of the vehicle brake system during anactuation of the brake pedal.

[0004] Because the pulsation-smoothing device is rather small, andespecially because the storage volume for the pulsation-smoothing devicecan be kept fairly small, it is advantageously also unnecessary toprovide a check valve downstream of the pulsation-smoothing device.Because this check valve is not necessary, the advantage is attainedthat the production cost and structural size of the vehicle brake systemof the invention can be kept small; there is also the advantage that theunnecessary additional check valve cannot become defective.

[0005] Because of the good damping of pressure fluctuations by thepulsation-smoothing device, the advantage is attained that substantiallyless noise is created, and the durability of the piston pump issubstantially better.

DRAWINGS

[0006] The drawing shows a detail of a hydraulic block of atraction-controlled vehicle brake system in the region of a piston pumpof the vehicle brake system. The sectional plane extends as alongitudinal section through the piston pump.

[0007] FIGS. 1-10 show a plurality of different, preferably selected andespecially advantageous exemplary embodiments.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

[0008] The pump assembly of the invention is intended in particular as apump in a brake system of a vehicle and is used to control the pressurein wheel brake cylinders. Depending on the type of brake system, theabbreviations ABS (for anti-lock brake system), TCS (traction controlsystem), VDC (vehicle dynamics control) and EHB (electrohydraulic brakesystem) are used for such brake systems. In the brake system, the pumpserves for instance to return brake fluid from a wheel brake cylinder ora plurality of wheel brake cylinders to a master cylinder (ABS) and/orto pump brake fluid out of a supply container into a wheel brakecylinder or a plurality of wheel brake cylinders (TCS or VDC or EHB). Ina brake system with wheel slip control (ABS or TCS) and/or a brakesystem serving as a steering aid (VDC) and/or an electrohydraulic brakesystem (EHB), for instance, the pump is needed. With wheel slip control(ABS or TCS), locking of the wheels of the vehicle during a brakingevent involving strong pressure on the brake pedal (ABS) and/or spinningof the driven wheels of the vehicle in the event of strong pressure onthe gas pedal (TCS) can for instance be prevented. In a brake systemserving as a steering aid (VDC), a brake pressure is built up in one ormore wheel brake cylinders independently of an actuation of the brakepedal or gas pedal, for instance to prevent the vehicle from breakingout of the track desired by the driver. The pump can also be used in anelectrohydraulic brake system (EHB), in which the pump pumps the brakefluid into the wheel brake cylinder or wheel brake cylinders if anelectric brake pedal sensor detects an actuation of the brake pedal, orin which the pump is used to fill a reservoir of the brake system.

[0009]FIG. 1 shows a first, especially advantageous, preferably selectedexemplary embodiment.

[0010]FIG. 1 shows a piston pump 1. The piston pump 1 is built into ahydraulic block, shown in part and in section, of the vehicle brakesystem. A plurality of piston pumps 1 can be built into the hydraulicblock. The hydraulic block forms a pump housing 2 of the piston pump 1.The piston pump 1 includes a bush 4, inserted into the pump housing 2,an eccentric element 6, an inlet connection 8, and an outflow conduit10. The inlet connection 8 and the outflow conduit 10 extend through thehydraulic block or pump housing 2. From the outflow conduit 10,branching lines not shown lead via hydraulic valves, not shown, to amaster cylinder and wheel brake cylinders, not shown. An installationchamber 12 is located in the pump housing 2. The bush 4 and a pumppiston 14 are inserted into the installation chamber 12. The pump piston14 has one end 14 a toward the eccentric element 6, and one end 14 bremote from the eccentric element 6. Via the eccentric element 6, thepump piston is successively driven to execute an intake stroke and acompression stroke in alternation.

[0011] The installation chamber 12 provided in the pump housing 2 issealed off from the outside by a closure piece 16. The closure piece 16has a bottom 17 on its face end, oriented outward. The bush 4 has abottom 18 on its end, toward the closure piece 16. A restoring spring 19braced on the bush bottom 18 and on the pump piston 14 keeps the end 14a of the pump piston 14 in contact with the eccentric element 6. Betweenthe bush bottom 18 and the end 14 b, remote from the eccentric element6, of the pump piston 14, there is a compression chamber 20 thatincreases in size during an intake stroke and decreases in size during acompression stroke.

[0012] The piston pump 1 has an inlet valve 22. The inlet valve 22 has avalve seat 22 a, a closing body 22 b, and a closing spring 22 c. Theclosing spring 22 c urges the closing body 22 b against the valve seat22 a provided on the pump piston 14.

[0013] The piston pump 1 has an outlet valve 24. The outlet valve 24 hasa valve seat 24 a, a closing body 24 b, a closing spring 22 c, and aretaining element 24 d. The closing spring 24 c urges the closing body24 b against the valve seat 24 a, which is structurally connected to thehousing and for instance is provided on the bush bottom 18. One end ofthe closing spring 24 c is braced on the closing body 24 a, and one endof the closing spring 24 c is braced on the retaining element 24 dstructurally connected to the housing. The retaining element 24 d issecured to the bottom 18 of the bush 4. The retaining element 24 bserves not only to brace the closing spring 24 c but also to guide theclosing body 24 b. The retaining element 24 d has at least one passageof adequate size, through which the pressure medium can flow.

[0014] An inlet passage 26 leads from the inlet connection 8 to theinlet valve 22. A passage 28 leads from the compression chamber 20through the bush bottom 18 to the outlet valve 24. The valve seat 24 asurrounds the passage 28.

[0015] On the side of the closing body 24 b remote from the passage 28,there is an outflow chamber 30. In other words, the outflow chamber 30is the chamber that adjoins the valve seat 24 a downstream. In theexemplary embodiment selected, the outflow chamber 30 is located betweenthe bush bottom 18 and the bottom 17 of the closure piece 16. Theclosing spring 24 c and the retaining element 24 d are located in theoutflow chamber 30.

[0016] An elastically resilient wall 32 is built in, inside theinstallation chamber 12. The elastically resilient wall 32 is locateddownstream of the valve seat 24 a, in the immediate vicinity of theoutlet valve 24. The outer circumference of the elastically resilientwall 32 is built in tightly and firmly inside the closure piece 16. Theresilient wall 32 is acted upon by the pressure prevailing in theoutflow chamber 30. On the side of the resilient wall 32 remote from theoutflow chamber 30, there is a counterpart chamber 36. Inside thecounterpart chamber 36, a gas is for instance tightly trapped. However,it is also possible for the counterpart chamber 36 to communicate withthe atmosphere via an opening 38.

[0017] A compressible body 34 is built into the outflow chamber 30, inthe immediate vicinity of the outlet valve 24. The compressible body 34is acted upon on one side by the pressure prevailing in the outflowchamber 30, and on the other side, the compressible body 34 ispredominantly braced against the resilient wall 32. The compressiblebody 34 covers the entire surface of the resilient wall 32. On its outercircumference, the compressible body 34 additionally serves to providesealing between the outflow chamber 30 and the counterpart chamber 36.The volume of the compressible body 34 is dimensioned to be great enoughthat at low-frequency pressure fluctuations in the outflow chamber 30,the volume of the compressible body 34 varies in accordance with thepressure pulsations, so that the pressure pulsations are intercepted bythe compressible body 34 and thus smoothed out. The compressible body 34is preferably made of rubber or an elastomer material. The compressiblebody 34 preferably has intrinsically minimally small gas-filled voids,so that upon pressure changes, a change in volume of the compressiblebody 34 can take place.

[0018] The compressible body 34 comprises a material of such a kind thatit has a volume that is variable as a function of pressure. A materialis selected that upon varying its volume dissipates some of the energyof the pulsations by means of internal friction.

[0019] The resilient wall 32 is preferably a relatively thin, platelikedisk of a springy material, preferably spring steel. The elasticity andresilience of the springy, resilient wall 32 is dimensioned such that athigh-frequency pressure pulsations in the outflow chamber 30, upon asudden pressure increase, the resilient wall 32 yields in the directionof the counterpart chamber 36, while upon a high-frequency, suddenpressure drop in the outflow chamber 30, the resilient wall 32 springsback in the direction of the outflow chamber 30. It is thus attainedthat high-frequency pressure pulsations are smoothed out in theimmediate vicinity, just downstream of the valve seat 24 a.

[0020] The outflow chamber 30 communicates with the outflow conduit 10via a throttle 39. The throttle 39 is disposed in the vicinity of theoutlet valve 24, close to the outlet valve 24. With the aid of thethrottle 39, it is attained that the pressure pulsations occurring inthe region of the outlet valve 24 inside the outflow chamber 30 act inconcentrated form on the resilient wall 32 and on the compressible body34. By means of the resilient wall 32 and the compressible body 34,pressure pulsations are prevented from occurring in the immediatelocation where the pulsations would otherwise occur, so that thepulsations cannot spread past the throttle 39 into the outflow conduit10.

[0021] In the exemplary embodiment shown in FIG. 1, the shape of theoutflow chamber 30 in cooperation with the elastically resilient wall32, the compressible body 34, the counterpart chamber 36, and thethrottle 39, forms a highly effective pulsation-smoothing device 40. Thecomponents of the pulsation-smoothing device 40 are preferably disposedin the immediate vicinity of the outlet valve 24. As a result, thehydraulic resilience of the pulsation-smoothing device 40 can be keptrelatively slight. This has the advantage that despite very goodpulsation smoothing, the hydraulic system in the outflow conduit 10 canbe kept fairly rigid, even without using an additional check valvedownstream of the pulsation-smoothing device 40.

[0022] By building the wall 32, the body 34, and the counterpart chamber36 into the closure piece 16, the advantage is attained that a smalltotal number of components is needed, and that the assembly of thepiston pump 1 can be accomplished without additional expense. Theclosure piece 16 is built into the installation chamber inpressure-tight fashion, by way of a crimped connection known per se. Theclosure piece 16 seals off the high-pressure region of the piston pump 1from the outside.

[0023]FIG. 2 shows a further, especially advantageous, preferablyselected exemplary embodiment.

[0024] In all the drawings, elements that are the same or function thesame are identified by the same reference numerals. Unless anything issaid to the contrary or shown to the contrary in the drawing, what issaid for and shown in one of the drawings applies to the others as well.Unless otherwise stated in the explanations, the details of theindividual exemplary embodiments and the various drawings can becombined with one another.

[0025] In the exemplary embodiment preferably shown in FIG. 2, aretaining element 42 is press-fitted into the closure piece 16. Theretaining element 42 keeps the resilient wall 32 in contact with ashoulder 44 provided on the closure piece 16. Between an annular endface 46 of the retaining element 42 and the resilient wall 32, acompressible annular body 48 is installed. The compressible annular body48 provides sealing between the outflow chamber 30 and the counterpartchamber 36. For the annular body 48, the same material as for thecompressible body 34 can be used.

[0026] At low-frequency pressure pulsations in the outflow chamber 30,the compressible annular body 48 is compressed radially outward upon apressure increase, while at low-frequency pressure drops, the annularbody 48 springs back radially inward. As a result, low-frequencypressure pulsations are eliminated, or at least damped considerably,directly in the outflow chamber 30.

[0027] In the exemplary embodiment shown in FIG. 2, the shape of theoutflow chamber 30, in cooperation with the wall 32 that is elasticallyresilient as a function of pressure, the compressible annular body 48,the counterpart chamber 36, and the throttle 39, forms the highlyeffective pulsation-smoothing device 40. The components of thepulsation-smoothing device 40 are preferably disposed in the immediatevicinity of the outlet valve 24.

[0028]FIG. 3 shows a further, especially advantageous, preferablyselected exemplary embodiment.

[0029] The resilient wall 32 can for instance, as shown in FIG. 2,comprise a single spring-elastic plate. However, as shown in FIG. 3, theresilient wall 32 can also preferably be assembled from a firstspring-elastic plate 32 a and a second spring-elastic plate 32 b. It isalso possible, however, to modify the exemplary embodiment in such a waythat the resilient wall 32 is put together from three plates restingflatly against one another and preferably compressed somewhat, or evenfour or more such plates. What in this case are at least twospring-elastic plates 32 a, 32 b are put together in such a way thatbetween them, a friction device 49 is created.

[0030] Upon high-frequency pressure pulsations in the outflow chamber30, the resilient wall 32 yields in the direction of the counterpartchamber 36, or back in the direction of the outflow chamber 30. Theresult is flexing of the resilient wall 32. Because of this flexing, thespring-elastic plates 32 a and 32 b shift relative to one another. Thiscreates a relative motion between the plates 32 a, 32 b, and because ofthe friction, damping occurs. The result is especially effective dampingof the high-frequency pressure pulsations in the outflow chamber 30.

[0031] In the exemplary embodiment shown in FIG. 3, the shape of theoutflow chamber 30, in cooperation with the elastically resilient wall32, the throttle 39, the annular body 48, the counterpart chamber 36,and the friction device 49, forms the highly effectivepulsation-smoothing device 40. The components of the pulsation-smoothingdevice 40 are preferably disposed in the immediate vicinity of theoutlet valve 24.

[0032] It is noted that the friction device 49 can be installed in theexemplary embodiments shown in the other drawings as well. Particularlyin FIGS. 1, 2, 4, 6 and 7, the elastically resilient wall 32 providedfor the sake of forming the friction device 49 can also be put togetherfrom a plurality of plates contacting one another and rubbing againstone another.

[0033]FIG. 4 shows a longitudinal section through a further, especiallyadvantageous, preferably selected exemplary embodiment.

[0034] In the exemplary embodiment shown in FIG. 4, the elasticallyresilient wall 32 is approximately in the form of a top hat. The outerrim of the elastically resilient wall 32 is press-fitted into theclosure piece 16. The counterpart chamber 36 communicates with theoutflow conduit 10 via a connection 51. The cross section of theconnection 51 is dimensioned such that the flow of pressure medium isthrottled somewhat in this connection 51. The connection 51 has aconnecting throttle 51a. However, the throttling action of the throttle39 is preferably substantially stronger than the throttling action ofthe connecting throttle 51 a.

[0035] Upon pressure pulsations in the outflow chamber 30, an elasticdeformation of the wall 32 occurs. In the elastic deformation of thewall 32, some of the energy upon pressure pulsations is intercepted bythe resilient wall 32. As a result, the pressure pulsations areattenuated substantially and cannot spread, or can spread only withsubstantial attenuation, via the throttle 39 into the outflow conduit10. The substantially attenuated pressure pulsations reaching theoutflow conduit 10 are operative through the connection 51 as far as thecounterpart chamber 36. Because of the travel distance and because ofthe throttle 39 as well as the connecting throttle 51 a that may beprovided in the connection 51, the pressure pulsations reach thecounterpart chamber 36 with a phase offset relative to the pressurepulsations in the outflow chamber 30. This reinforces the elasticflexing of the resilient wall 32, so that because of the pressurepulsations in phase opposition in the counterpart chamber 36, anespecially effective breakdown of pressure pulsations in the outflowchamber 30 results. As a result, the pressure pulsations are broken downespecially effectively, and a very uniform flow of pressure medium isobtained in the outflow conduit 10.

[0036] In the exemplary embodiment shown in FIG. 4, the shape of theoutflow chamber 30, along with the elastically resilient wall 32, thecounterpart chamber 36, the throttle 39, and the connection 51connecting the counterpart chamber 36 with the outflow conduit 10, formthe highly effective pulsation-smoothing device 40. The components ofthe pulsation-smoothing device 40 are preferably disposed in theimmediate vicinity of the outlet valve 24.

[0037]FIG. 5 shows a further selected, especially advantageous exemplaryembodiment.

[0038] The outlet valve 24, on the side of the closing body 24 b remotefrom the passage 28, has a rear valve chamber 53.

[0039] In the exemplary embodiment shown in FIG. 5, the ball-shapedclosing body 24 b of the outlet valve 24 is guided in the openingdirection along a constriction in the closure piece 16. The constrictionbetween the closing body 24 b and the closure piece 16 is so narrow thatat most an insignificant, negligibly small fluidic communication existsbetween the rear valve chamber 53 and the outflow chamber 30. Becausethe constriction disconnects the outflow chamber 30 from the rear valvechamber 53, this constriction will hereinafter be called thedisconnection point 52.

[0040] A passage 50 connects the outflow conduit 10 with the rear valvechamber 53.

[0041] In the preferably selected exemplary embodiment, the passage 50is composed of one longitudinal groove 50 a or a plurality oflongitudinal grooves 50 a, one circumferential groove 50 b, and oneradial hole 50 c or a plurality of radial holes 50 c. Thecircumferential groove 50 b communicates with the outflow conduit 10 viathe at least one longitudinal groove 50 a and with the rear valvechamber 53 via the at least one radial hole 50 c. If the closing body 24b vibrates, which could cause a pressure pulsation in the outflowchamber 30, pressure medium is exchanged between the rear valve chamber53 and the outflow conduit 10. In this process, the pressure mediumflows through the passage 50, which has multiple right angles. Theseright angles engender an advantageous resistance, which assures that inthe rear valve chamber 53, pressure fluctuations oriented counter tovibration of the closing body 24 b will build up, which assure effectivedamping of the vibration of the closing body 24 b. As a result, andespecially also in cooperation with the throttle 39 between the outflowconduit 10 and the outflow chamber 30, it is assured that any pressurepulsations that occur will be effectively reduced, and in particularthat any pressure pulsations that occur will not reach the outflowconduit 10.

[0042] Between the outflow chamber 30 and the outflow conduit 10, thethrottle 39 is preferably provided, which additionally contributes tosmoothing pressure pulsations. The throttle 39 has an especiallypulsation-damping effect if it is disposed fairly tightly in the regionof the valve seat 24 a.

[0043] In the exemplary embodiment shown in FIG. 5, the shape of theoutflow chamber 30, in cooperation with the rear valve chamber 53, thethrottle 39, and the passage 50, forms the highly effectivepulsation-smoothing device 40. The components of the pulsation-smoothingdevice 40 are preferably disposed in the immediate vicinity of theoutlet valve 24.

[0044]FIG. 6 shows a further especially selected, especiallyadvantageous exemplary embodiment.

[0045] In the exemplary embodiment shown in FIG. 6, a barometric cell 54is inserted into the interior of the closure piece 16 and thus into theinstallation chamber 12. The barometric cell 54 preferably shown forinstance comprises a first wall 54 a and a second wall 54 b. The twowalls 54 a, 54 b are joined in pressure-tight fashion to one another ontheir circumference, preferably being welded together. As a result, inthis exemplary embodiment, the counterpart chamber 36 between the twowalls 54 a, 54 b is hermetically sealed off from the outside. In thecounterpart chamber 36, there is preferably a readily compressible gas,such as air. The barometric cell 54 is inexpensive to produce anddurably assures a sealed enclosure of a gas volume.

[0046] The first wall 54 a, toward the outflow chamber 30, forms theelastically resilient wall 32. Because of the elastically resilient wall32, the outflow chamber 30 enlarges somewhat upon pressure pulsationsduring a pressure increase, so that the pressure increase issubstantially less forceful than if the elastically resilient wall 32were not present. During a pressure drop, the elastically fastened wall32 springs back in the direction of the outflow chamber 30, so that thepressure drop in the outflow chamber 30 is not so forceful as if theelastically resilient wall 32 were not present. The throttle 39 assuresthat the pressure fluctuations are essentially limited to the outflowchamber 30, where because of the elastically resilient wall 32 aneffective smoothing of the pressure fluctuations occurs. As a result, itis attained that a flow with effectively smoothed pressure fluctuationsis present in the outflow conduit 10.

[0047] In this exemplary embodiment as well, a friction device thatadditionally damps vibration can be provided, as shown in FIG. 2, forinstance by providing that the first wall 54 a is composed of two platesresting on one another.

[0048] In the exemplary embodiment shown in FIG. 6, the shape of theoutflow chamber 30, in cooperation with the elastically resilient wall32, the counterpart chamber 36, the throttle 39, and the barometric cell54, forms the highly effective pulsation-smoothing device 40. Thecomponents of the pulsation-smoothing device 40 are preferably disposedin the immediate vicinity of the outlet valve 24.

[0049]FIG. 7 shows a further preferably selected, especiallyadvantageous exemplary embodiment.

[0050]FIG. 7 differs from FIG. 6 in having a compressible body 55 thatdamps vibration.

[0051] It has been demonstrated that by incorporating the compressiblebody 55 into the outflow chamber 30, pressure pulsations can be smoothedeven better. The compressible body 55 is especially effective if, on thedownstream side, it is located as close as possible to the outlet valve24, in its immediate vicinity. By inserting the compressible body 55shown in FIG. 7 into the outflow chamber 30, an additionalcompressibility in the outflow chamber 30 is obtained. As a result,despite the insertion of the compressible body 55 into the outflowchamber 30, the structural size overall can be kept substantiallysmaller than without the compressible body 55, and substantially bettersmoothing of the pressure pulsations is obtained.

[0052] In the exemplary embodiment shown in FIG. 7, the shape of theoutflow chamber 30, in cooperation with the elastically resilient wall32, the counterpart chamber 36, the throttle 39, the barometric cell 54,and the compressible body 55, forms the highly effectivepulsation-smoothing device 40. The components of the pulsation-smoothingdevice 40 are preferably disposed downstream of and in the immediatevicinity of the outlet valve 24.

[0053]FIG. 8 shows a further preferably selected, especiallyadvantageous exemplary embodiment.

[0054] The exemplary embodiment shown in FIG. 8 corresponds extensivelyto the exemplary embodiments shown in the other drawings, except for thedifferences named below. In particular, however, the piston pump shownin FIG. 8 is largely equivalent to the piston pump shown in FIG. 5.

[0055] In the exemplary embodiment shown in FIG. 8, a resilient wall 56is sealingly inserted into the circumferential groove 50 b of thepassage 50. Because of the elastic deformation of the resilient wall 56,resulting from pressure pulsations in the rear valve chamber 53 causedby vibration of the closing body 24 b, damping of the pressurefluctuations arising in the rear valve chamber 53 is obtained. Theresult is a calming of the vibration of the closing body 24 b. As aresult, the flow of pressure medium flowing through the outlet valve 24and the outflow chamber 30 into the outflow conduit 10 is also calmed,so that overall, substantially weaker pressure fluctuations arise.

[0056] In the exemplary embodiment shown in FIG. 8, the shape of theoutflow chamber 30, in cooperation with the throttle 39, the passage 50,the rear valve chamber 53, and the dampingly resilient wall 56, formsthe highly effective pulsation-smoothing device 40. The components ofthe pulsation-smoothing device 40 are preferably disposed downstream ofand in the immediate vicinity of the outlet valve 24.

[0057]FIG. 9 shows a further preferably selected, especiallyadvantageous exemplary embodiment.

[0058] The piston pump 1 shown as an example in FIG. 9 is essentiallyequivalent, except for the differences listed, to the piston pumps 1shown as examples in the other drawings.

[0059] In the exemplary embodiment shown in FIG. 9, an insert 58 isincorporated into the installation chamber 12, between the closure piecebottom 17 and the bush bottom 18.

[0060] Between the outflow chamber 30 and the outflow conduit 10, aturbulence-causing throttle 60 is provided. The pressure medium flowingfrom the outlet valve 24 through the outflow chamber 30 to the outflowconduit 10 must pass through the turbulence-causing throttle 60.Beginning at the outflow chamber 30, the turbulence-causing throttle 60for instance comprises one radial groove 60 a or a plurality of radialgrooves 60 a provided at the insert 58, a circumferential groove 60 bmade on the insert 58, one oblong slot 60 c or a plurality of oblongslots 60 c made in the insert 58, a second circumferential groove 60 d,one radial conduit 60 e or a plurality of radial conduits 60 e, a thirdcircumferential groove 60 f, and one longitudinal conduit 60 g or aplurality of longitudinal conduits 60 g. The at least one radial groove60 a and the circumferential groove 60 b are located on the face end ofthe insert 58 toward the bush bottom 18. The second circumferentialgroove 60 d, the at least one radial conduit 60 e, and the thirdcircumferential groove 60 f are located in the face end of the insert 58toward the closure piece bottom 17. The at least one longitudinalconduit 60 g is preferably machined into an inner circumferential faceof the closure piece 16. The at least one radial groove 60 a connectsthe outflow chamber 30 with the circumferential groove 60 b. The atleast one oblong slot 60 c connects the two circumferential grooves 60b, 60 d to one another. The at least one radial conduit 60 e connectsthe two circumferential grooves 60 d, 60 f to one another. The at leastone longitudinal conduit 60 g connects the third circumferential groove60 f with the outflow conduit 10.

[0061] Because the flow of pressure medium through theturbulence-causing throttle 60 is deflected many times, and because theturbulence-causing throttle 60 has quite different cross sections in thecourse of the flow path, and as a result the flow of pressure mediummust flow at quite different flow speeds and in quite differentdirections and with sudden deflections, the overall result is a markedreduction in pulsations within the flow of pressure medium flowing fromthe outlet valve 24 into the outflow conduit 10; that is, it is assuredthat virtually no pressure pulsations can occur.

[0062] The essential parts of the turbulence-causing throttle 60 arelocated on the insert 58 that is easy to produce, or in the insert 58that is easy to produce. This has the advantage that despite theturbulence-causing throttle 60, no complicated machining operations onthe other parts of the piston pump 1 are necessary.

[0063] The rear valve chamber 53 communicates with the outflow chamber30 only via the disconnection point 52 that allows only very little orpractically no pressure medium to pass through it. Upon vibration of theclosing body 24 b, pressure fluctuations that are oriented directlycounter to a vibration of the closing body 24 b are engendered in therear valve chamber 53. The result is a pronounced calming of thevibration of the closing body 24 b. This result is a substantially moreuniform hydraulic flow out of the outflow chamber 30 into the outflowconduit 10.

[0064] In the exemplary embodiment shown in FIG. 9, the shape of theoutflow chamber 30 in cooperation with the rear valve chamber 53, thedisconnection point 52 and the turbulence-causing throttle 60 form thehighly effective pulsation-smoothing device 40. The components of thepulsation-smoothing device 40 are preferably disposed downstream of andin the immediate vicinity of the outlet valve 24.

[0065]FIG. 10 shows a further preferably selected, especiallyadvantageous exemplary embodiment.

[0066] Except for the differences shown or described below, the pistonpump 1 shown in FIG. 10 is essentially equivalent to the piston pumps 1shown in the other drawings. In particular, the piston pump 1 shown inFIG. 10 is largely equivalent to the piston pump 1 shown in FIG. 9.

[0067] In the exemplary embodiment shown in FIG. 10, the circumferentialgroove 60 d of the turbulence-causing throttle 60 is widened radiallyinward so far that the circumferential groove 60 d changes over into therear valve chamber 53. As a result, the pressure medium flowing throughthe turbulence-causing throttle 60 is calmed, and the partially calmedpressure medium acts on the closing body 24 in the rear valve chamber53, on the side of the closing body 24 b remote from the passage 28.Because the flow of pressure medium is partly calmed by theturbulence-causing throttle 60, substantial damping of the vibration ofthe closing body 24 b results. In the further flow of pressure mediumout of the circumferential groove 60 d in the direction of the outflowconduit 10, a further, additional calming of the flow of pressure fluidand a further breakdown of pressure peaks then occur.

[0068] In the exemplary embodiment shown in FIG. 10, the shape of theoutflow chamber 30, along with the rear valve chamber 53, thedisconnection point 52, the turbulence-causing throttle 60, and thehydraulic communication of the rear valve chamber 53 with theturbulence-causing throttle 60, form the highly effectivepulsation-smoothing device 40. The components of the pulsation-smoothingdevice 40 are preferably disposed downstream of and in the immediatevicinity of the outlet valve 24.

1. A piston pump, having a pump piston (14) supported displaceably in apump housing (2), having an inlet valve (22), having an outlet valve(24), and having a compression chamber (20) provided between the inletvalve (22) and the outlet valve (24) in the pump housing (2), whichchamber increases in size upon an intake stroke of the pump piston (14)and decreases in size upon a compression stroke of the pump piston (14),characterized in that a pulsation-smoothing device (40) is disposed inthe region of the outlet valve (24).
 2. The piston pump of claim 1,characterized in that the pulsation-smoothing device (40) is disposedspatially in the immediate vicinity of the outlet valve (24).
 3. Thepiston pump of claim 1 or 2, characterized in that the outlet valve (24)has an outflow chamber (30).
 4. The piston pump of claim 3,characterized in that a resilient wall (32) defines the outflow chamber(30).
 5. The piston pump of claim 4, characterized in that a frictiondevice (49) is provided on the resilient wall (32). (FIG. 3)
 6. Thepiston pump of one of claims 3-5, characterized in that a compressiblebody (34, 48, 55) is provided in the outflow chamber (30). (FIGS. 1, 2,3, 7)
 7. The piston pump of one of claims 3-6, characterized in that adamping body (34, 48, 55) is provided in the outflow chamber (30).(FIGS. 1, 2, 3, 7)
 8. The piston pump of one of claims 3-7,characterized in that a throttle (39) is provided downstream of theoutflow chamber (30).
 9. The piston pump of claim 8, characterized inthat an outflow conduit (10) of the piston pump (1) communicatesdownstream of the throttle (39), via a connection (51), with acounterpart chamber (36) adjoining the elastically resilient wall (32).(FIG. 4)
 10. The piston pump of claim 9, characterized in that aconnecting throttle (51 a) is disposed between the outflow conduit (10)and the counterpart chamber (36). (FIG. 4)
 11. The piston pump of one ofthe foregoing claims, characterized in that the outlet valve (24) has aclosing body (24 b) and an inlet side (28), and that a rear valvechamber (53) is located on a side of the closing body (24 b) toward theinlet side (28), and that a disconnection point (52) is provided betweenthe outflow chamber (30) and the rear valve chamber (53). (FIGS. 5, 8,9,10)
 12. The piston pump of claim 11, characterized in that the rearvalve chamber (53) communicates with the outflow conduit (10) via apassage (50). (FIGS. 5, 8)
 13. The piston pump of claim 12,characterized in that a throttle is provided in the passage (50). 14.The piston pump of claim 12 or 13, characterized in that a resilientwall (56) is provided in the passage (50). (FIG. 8)
 15. The piston pumpof one of the foregoing claims, characterized in that aturbulence-causing throttle (60) is disposed between the outflow chamber(30) and the outflow conduit (10). (FIGS. 9,10)
 16. The piston pump ofclaim 15, characterized in that the rear valve chamber (53) communicateswith the outflow chamber (30) via at least a portion of theturbulence-causing throttle (60). (FIG. 10)
 17. The piston pump of oneof the foregoing claims, characterized in that a barometric cell (54)containing a compressible counterpart chamber (36) is disposed in theoutflow chamber (30). (FIGS. 6, 7)